(Not Applicable)
(Not Applicable)
1. Technical Field
The inventive arrangements relate generally to methods and apparatus providing advanced operating features for programs recorded on disc media, for example recordable digital video discs, hard drives and magneto optical discs.
2. Description of the Related Art
While conventional trick modes enable a user to view recorded video at different speeds, the video is not permanently altered by the process. If the video is displayed at a later time, then the user must initiate another trick mode to view the video at a different speed. Significantly, however, many users may wish to permanently change the playback speed of a particular portion of video by modifying the video once the video has been recorded onto the media. Such a process can permit speed variations during playback without the user invoking a trick mode command. Unfortunately, several significant obstacles exist that make editing recorded video in such a fashion impracticable.
For example in the case of media such as magnetic tape and optical disc media such as DVD, it is desirable to record program data in a contiguous manner on the medium so as to avoid interruptions in program presentation. Typically, however, the space occupied by the original recorded video is not large enough to store the pictures that must be repeated in order to produce certain trick effects such as slow motion playback. This makes it difficult to store a modified video segment in the same physical location as the original data. In addition to spatial limitations, repeating pictures on the disc or other media can interfere with the conventional picture structure of the video, which can degrade the display quality of the video during playback.
Modifying recorded video to produce fast-forward playback, however, is not affected by the spatial limitations that impede slow-motion editing. This is because fast-forward editing typically deletes pictures from the recorded video. Nevertheless, creating fast-forward video, similar to slow-motion modification, also negatively impacts the conventional picture structure of the video.
Performing trick modes on video recorded under a non-progressive scanning format, particularly when a moving object is recorded, can present another problem as well. Non-progressive frames are not progressively scanned but are actually two interlaced fields that have been merged to create a frame. Each interlaced field contains roughly one-half the picture information typically contained in a complete frame. These interlaced fields, however, are temporally distinct, and moving objects will appear in a different location in each field. Thus, if the fields are combined to form a non-progressive frame, a moving object will appear elongated.
In a number of high-performance televisions, the fields from a non-progressive frame are separated and deinterlaced to form two complete frames. As such, a moving object will appear in a different location in the newly created frames. During trick mode playback, the frames created from the deinterlacing process are typically alternately repeated and displayed. This can cause moving objects in the display to appear to jump, or vibrate, from one location to another resulting in an unwanted artifact.
Thus, what is needed is a device that can change the playback speed of video recorded under a non-progressive scanning format yet can overcome the spatial and structural limitations associated with such recorded video. Moreover, such a device must avoid the unwanted vibration artifact that is associated with this type of recorded video during trick mode playback.
In a rewritable storage medium, the invention includes a method for changing a playback speed of a selected video segment having a non-progressive frame structure which has been recorded on a portion of the storage medium. In one arrangement, the invention includes the steps of: modifying the selected video segment for a changed playback speed; and recording the modified video segment exclusively on the portion of the medium. The invention can also include the step of deleting a plurality of non-video packs in the selected video segment to reduce an amount of data contained in the modified video segment. Further, the invention can also include the steps of reducing a resolution of at least one frame contained in the modified video segment and lowering a bit rate of the modified video segment during the recording step.
In one arrangement of the above invention, the video segment can be comprised of intra and non-intra frames and the modification can comprise the steps of: decoding the intra and non-intra frames; reencoding the intra and non-intra frames into their associated field pictures; and inserting at least one of the group consisting of dummy field pictures and repeat field pictures into the selected video segment. In addition, the number of dummy field pictures and repeat field pictures inserted into the selected video segment can be based on the changed playback speed. Moreover, the invention can include the step of selectively decoding and reencoding the modified video segment for conventional placement of the dummy field pictures, the repeat field pictures and the associated field pictures.
In another arrangement of the above method, the video segment can be comprised of intra and non-intra frames and the modification can include the step of removing at least one frame from the group consisting of the intra and non-intra frames. Alternatively, the video segment can include intra and non-intra frames, and the modification can include the steps of: decoding the intra and non-intra frames; and removing at least one field picture from at least one of said intra and non-intra frames.
In another arrangement, the invention includes a system for changing a playback speed of a selected video segment having a non-progressive frame structure recorded on a rewritable storage medium. The above system includes: storage medium circuitry for selectively reading a video segment which has been recorded on a portion of the rewritable storage medium; a video processor for modifying the selected video segment for a changed playback speed; and video recording circuitry for recording the modified video segment exclusively on the portion of the storage medium. The system also includes suitable software and circuitry to implement the method as described above.